1. Field of the Invention
The present invention pertains to purlin-rafter interconnection systems and, more particularly, to purlin-rafter interconnection systems using locking elements therebetween.
2. History of the Prior Art
The interconnection of purlins and rafters in the construction of buildings and roofs is a well developed art. Of primary concern in such interconnection system is the maintenance of the structural integrity of both the rafter and the purlin as well as the interconnection therebetween. Because the more conventional purlin and rafters of skylights are constructed from extruded aluminum, this interconnection is often quite difficult from an assembly standpoint. Complex mounting techniques include special notches and the removal of various structural sections in either the purlin or the rafter. Although notches and/or apertures in the purlin or rafter can be accommodated without adverse structural affect, it is preferable to minimize these modifications to the structural members. Consistent therewith it is important to minimize the amount of field labor required to effect the intersection of the structural members during the erection process. For this reason, many advanced skylights systems incorporate purlin and rafter designs which integrate structural integrity and ease in assembly in a configuration that is economically fabricated. The designs of such configurations are, however, limited by many applications.
Some of the prior art approaches to purlin-rafter interconnections are seen in U.S. Pat. Nos. 3,844,087 and 4,455,798. In each of these patent references, the purlin intersects the rafter with a simple interconnection technique incorporating in some instances a minimum of additional connection elements. For example, in the Schultz U.S. Pat. No. 3,844,087, a skylight structure is shown with a plurality of interconnection pins for interconnecting the purlin and rafters. The pins are secured in apertures in the purlin and project downwardly into the rafter condensate channels to abut the outer condensate channel walls. Longitudinally extending pins may also be inserted into holes where space is formed in the purlins. A notch 57 may likewise be formed in the outer rafter condensate channel to facilitate interconnection of the purlin and rafter. In the Tsakoris U.S. Pat. No. 4,455,798, a purlin-to-rafter tie is shown in the form of a locating pin 154 which includes a top section 156 which is of generally square cross-section and a lower narrow ribbed section 158. A rafter is provided with a transverse channel 164 disposed at a position along the rafter where the purlin is to be secured. Channel 164 is adapted to align with an elongated groove in an adjacently disposed purlin. Upright walls 166 define groove 165 into which the ribbed bottom section 158 of the locating pin is disposed.
Other forms of purlin and rafter interconnection systems have been devised in the prior art. In the main, these require substantial modification to either the purlin or the rafter or the interconnection therebetween. Additionally, the connecting members are sufficiently complex design so as to require particular tools and/or teachings for assembly. In many applications the simplicity of the installation in conjunction with the structural integrity thereof is the critical aspect. For this reason it would be an advance over the prior art to provide such an interconnection system facilitating simplicity in design and ease in assembly.
The present invention provides such an interconnection system by incorporating an overhanging lip cut in a first frontal face of a purlin and the utilization of a lock and key member in a central extrusion of the purlin to engage a transverse groove through a support rafter. Engagement is effected by a driven generally T-shaped key of, e.g., molded aluminum, plastic, or any similar material, which slides through the central extrusion portion of the purlin and interlocks with the transverse groove of the load bearing rafter. The key may include a projecting portion to facilitate the engagement and to prevent disengagement.